Note 14 - Stock Based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Notes Tables

Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block]

January 1,	Number of shares
2012		2,502
2013		2,871
2014		4,128
2015		5,463
2016		7,257
2017		12,623
2018		106,076
2019		233,862
Total additional shares		374,782

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	Year ended December 31,
	2019			2018
Risk free interest rate	2.16%	-	2.20%	2.47%	-	2.71%
Expected term (in years)	5.00	-	5.94	5.24	-	5.57
Dividend yield		0%			0%
Expected volatility	106.88%	-	126.16%	108.81%	-	126.43%

	January 13, 2019
Risk free interest rate		2.53	%
Expected term (in years)	4.5	-	5.0
Stock price	$	1.36
Dividend yield		-	%
Expected volatility	121.0	-	123.0%

Share-based Payment Arrangement, Option, Activity [Table Text Block]

	Number of Underlying Shares		Weighted- Average Exercise Price Per Share		Weighted- Average Contractual Life Remaining in Years		Aggregate Intrinsic Value
Outstanding as of January 1, 2019		783,383	$	12.14			$
Granted		3,565,000		1.51				3,667,300
Forfeited		(40,000)		2.38
Outstanding as of December 31, 2019		4,308,383		3.44		9.04	$	651,000
Exercisable as of December 31, 2019		3,500,186		3.74		9.05	$	569,625
Vested and expected to vest		4,308,383		3.44		9.04	$	651,000

Share-based Payment Arrangement, Option [Member]

Notes Tables

Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block]

	Year Ended December 31,
	2019		2018
General and administrative	$	4,656,963	$	809,110
Research and development		2,445,156		244,386
Total stock compensation expense	$	7,102,119	$	1,053,496

	Year Ended December 31, 2018
General and administrative	$	869,515
Research and development		540,510
Total stock compensation expense	$	1,410,025

	Year Ended December 31, 2019
General and administrative	$	1,074,183
Research and development		667,736
Total stock compensation expense	$	1,741,919